JP2016143505A - Positive electrode plate for nonaqueous electrolyte power storage element and nonaqueous electrolyte power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing degradation of durability and an output/input characteristic in a high temperature area within a normal use temperature zone by increasing the increase start temperature of inner resistance in a positive electrode plate for a nonaqueous electrolyte power storage element which increases the internal resistance when the temperature exceeds the normal use temperature zone.SOLUTION: In a positive electrode plate for a nonaqueous electrolyte power storage element, an intermediate layer containing conductive agent and fluorine-contained resin binder is provided between a positive electrode collector and a positive electrode mixture layer, and the porosity of the positive electrode mixture layer is set to 39% or less, whereby the increase start temperature of the inner resistance can be increased, and degradation in durability and output/input characteristic in a high temperature range within a normal use temperature zone can be suppressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positive electrode plate for a nonaqueous electrolyte storage element. The present invention also relates to a non-aqueous electrolyte storage element including the positive electrode plate for a water electrolyte storage element.

  Nonaqueous electrolyte storage elements such as nonaqueous electrolyte secondary batteries and lithium ion capacitors are frequently used as power supplies or auxiliary power supplies. In particular, nonaqueous electrolyte secondary batteries are widely used as power sources for electronic devices, automobiles, and the like because they can cope with size reduction, weight reduction, thickness reduction, energy density, and the like.

  Nonaqueous electrolyte storage elements are required to have high safety in addition to excellent performance such as charge / discharge characteristics and energy density. In particular, when the nonaqueous electrolyte storage element is overcharged due to erroneous operation, unauthorized use, or the like, a situation in which the temperature inside the storage element rises beyond the normal use temperature range is also assumed. Therefore, safety measures against overcharging of the nonaqueous electrolyte storage element are particularly important.

  Conventionally, various safety measures against overcharging of nonaqueous electrolyte storage elements have been studied. For example, Patent Document 1 discloses a case where the temperature inside the battery is increased due to overcharge by providing a conductive layer containing a conductive agent and specific polyvinylidene fluoride between the current collector and the electrode mixture. It has been reported that the internal resistance is increased to interrupt the current between the current collector and the electrode mixture, thereby preventing overheating.

JP 2012-104422 A

  When a conductive layer containing a conductive agent and polyvinylidene fluoride is provided between the current collector and the electrode mixture as in Patent Document 1, the conductive layer is overcharged when the internal resistance rise start temperature is low. Even if not, there is a concern that the internal resistance increases when used in a high temperature range within the normal use temperature range, and the durability and input / output characteristics decrease.

  Therefore, an object of the present invention is to provide a technique for increasing the temperature at which internal resistance rises in a positive electrode plate for a nonaqueous electrolyte storage element that raises internal resistance when it exceeds a normal use temperature range.

  The present inventor has intensively studied to solve the above-mentioned problems. As a result, in the positive electrode plate for a nonaqueous electrolyte storage element, a conductive agent and a fluorine-containing resin binder are interposed between the positive electrode current collector and the positive electrode mixture layer. In addition, by increasing the porosity of the positive electrode mixture layer to 39% or less, it is possible to increase the temperature at which the internal resistance starts rising, and durability and input / output in a high temperature range within the normal use temperature range. It has been found that it is possible to suppress deterioration of characteristics. The present invention has been completed by further studies based on such knowledge.

  That is, one aspect of the positive electrode plate for a nonaqueous electrolyte storage element of the present invention is a positive electrode current collector, a positive electrode mixture layer containing a positive electrode active material, and between the positive electrode current collector and the positive electrode mixture layer. An intermediate layer positioned, the intermediate layer including a conductive agent and a fluorine-containing resin binder, wherein the positive electrode mixture layer has a porosity of 39% or less. By providing such a configuration, it is possible to increase the rise start temperature of the internal resistance and suppress the deterioration of the durability and input / output characteristics in a high temperature range within the normal use temperature range.

Moreover, in the suitable one aspect | mode of the positive electrode plate for nonaqueous electrolyte electrical storage elements of this invention, the porosity of the said positive mix layer is set to 15 to 39%. Furthermore, in a preferred embodiment of the positive electrode plate for a non-aqueous electrolyte storage element of the present invention, polyvinylidene fluoride is used as the fluorine-containing resin binder. Moreover, in the suitable one aspect | mode of the positive electrode plate for nonaqueous electrolyte electrical storage elements of this invention, the application mass of the said positive mix layer is set to 0.5-2.5 g / 100cm < ² >. By providing such a configuration, it is possible to increase the internal resistance rise start temperature more effectively.

  Moreover, one aspect of the nonaqueous electrolyte storage element of the present invention is characterized by comprising the positive electrode plate for a nonaqueous electrolyte storage element. Furthermore, one mode of the power storage device of the present invention includes the nonaqueous electrolyte power storage element. By providing such a configuration, it is possible to provide a nonaqueous electrolyte electricity storage element and an electricity storage device that can increase the rise start temperature of internal resistance and suppress deterioration in durability and input / output characteristics in a high temperature range within a normal use temperature range. Is possible.

  ADVANTAGE OF THE INVENTION According to this invention, in the positive electrode plate for nonaqueous electrolyte electrical storage elements which raises internal resistance when it exceeds a normal use temperature range, increase start temperature of internal resistance can be raised.

It is a figure which shows the cross-section of the one aspect | mode of the positive electrode plate of this invention. It is a figure which shows the schematic of the rectangular nonaqueous electrolyte electrical storage element which is one aspect | mode of the nonaqueous electrolyte electrical storage element of this invention. It is a figure which shows the schematic of the one aspect | mode of the electrical storage apparatus of this invention.

1. Positive electrode plate for nonaqueous electrolyte storage element The positive electrode plate of the present invention is a positive electrode plate used as a positive electrode of a nonaqueous electrolyte storage element. A cross-sectional view of one embodiment of the positive electrode plate of the present invention is shown in FIG. As shown in FIG. 1, the positive electrode plate of the present invention has a structure having a positive electrode current collector 11, an intermediate layer 12 in contact with the positive electrode current collector, and a positive electrode mixture layer 13. The positive electrode plate of the present invention is characterized in that the intermediate layer contains a conductive agent and a fluorine-containing resin binder, and the porosity of the positive electrode mixture layer is 39% or less. Hereinafter, the positive electrode plate of the present invention will be described in detail.

[Positive electrode current collector]
Although it does not restrict | limit especially as a positive electrode electrical power collector used for the positive electrode plate of this invention, For example, metal materials, such as aluminum and the alloy containing the metal; Carbonaceous materials, such as carbon cloth and carbon paper, etc. are mentioned. Among these, aluminum is preferable.

[Middle layer]
In the positive electrode plate of the present invention, the intermediate layer is disposed between the positive electrode current collector and the positive electrode mixture layer. The intermediate layer contains a conductive agent and a fluorine-containing resin binder. By providing such an intermediate layer, it is possible to increase the internal resistance when the normal use temperature range is exceeded.

  The conductive agent used for the intermediate layer is not particularly limited as long as it is a conductive material. For example, carbon materials such as acetylene black, carbon black, ketjen black, carbon whisker, and carbon fiber: metal ( (Aluminum, silver, gold, etc.) metal materials such as powder and metal fibers; conductive ceramic materials and the like. Among these conductive agents, from the viewpoints of coatability and conductivity, carbon materials are preferable, and acetylene black is more preferable. These electrically conductive agents may be used individually by 1 type, and may be used in combination of 2 or more type.

The bulk density of the conductive agent is not particularly limited, but is preferably 1.0 g / cm ³ or less. If the bulk density of the conductive agent is 1.0 g / cm ³ or less, the conductive agent will come into contact with more binder, effectively suppressing the outflow of the binder of the intermediate layer to the positive electrode mixture layer. When the temperature exceeds the normal operating temperature range, the change width of the resistance of the positive electrode plate accompanying the swelling of the binder is increased, which is preferable. More preferably, it is 0.6 g / cm ³ or less, and further preferably 0.06 g / cm ³ or less. Moreover, it is preferable that the bulk density of a electrically conductive agent is 0.01 g / cm < ³ > or more from a viewpoint of ensuring the workability of an electrode. The bulk density is a value measured based on the method described in JIS K 1469.

The specific surface area of the conductive agent is not particularly limited, but is preferably 5.0 m ² / g or more. More preferably, it is 30 m < ² > / g or more, More preferably, it is 60 m < ² > / g or more. By satisfying such a specific surface area, the conductive agent comes into contact with more binder, and the outflow of the binder of the intermediate layer to the positive electrode mixture layer can be effectively suppressed. When the contact surface of the binder increases and exceeds the normal use temperature range, the change width of the resistance of the positive electrode plate accompanying the swelling of the binder becomes large, which is preferable. Moreover, it is preferable that the specific surface area of a electrically conductive agent is 1000 m < ² > / g or less from a viewpoint of ensuring the workability of an electrode. More preferably, it is 200 m < ² > / g or less, More preferably, it is 100 m < ² > / g or less. The specific surface area is a BET specific surface area measured by a nitrogen adsorption method using a multipoint method (relative vapor pressure is 0.05 to 0.2).

  In the intermediate layer, the content of the conductive agent is not particularly limited. For example, the conductive agent is 10% by mass or more, preferably 20 to 90% by mass, more preferably 20 to 50% by mass, based on the total amount of the intermediate layer. Can be mentioned.

  The type of the fluorine-containing resin binder used in the intermediate layer is not particularly limited as long as it can be used as a binder. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride- Examples thereof include vinylidene fluoride-containing copolymers such as hexafluoropropylene copolymer, and fluororubber. These fluorine-containing resin binders may be used alone or in combination of two or more. Among these fluorine-containing resin binders, polyvinylidene fluoride is preferably used from the viewpoint of further effectively increasing the temperature at which internal resistance starts to rise.

  In the intermediate layer, the content of the fluorine-containing resin binder is not particularly limited, but for example, the fluorine-containing resin binder is 90% by mass or less, preferably 10 to 80% by mass, more preferably 50 to 50%, based on the total amount of the intermediate layer. 80 mass% is mentioned. By satisfying such a range, the resistance value during normal operation can be kept low.

  In the intermediate layer, in addition to the conductive agent and the fluorine-containing resin binder, additives such as a thickener and a filler may be contained as necessary. Further, the intermediate layer may contain a positive electrode active material contained in the positive electrode mixture layer as long as the effects of the present invention are not impaired.

  Examples of the thickener include polysaccharides such as carboxymethylcellulose (CMC) and methylcellulose. These thickeners may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the filler include olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, and carbon. These fillers may be used individually by 1 type, and may be used in combination of 2 or more type.

  The thickness of the intermediate layer is, for example, 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. By satisfying such a range, the resistance value can be kept low at the temperature during normal operation. Further, the lower limit value of the thickness of the intermediate layer is not particularly limited, and examples thereof include 0.1 μm or more.

  The intermediate layer kneaded the constituent components into a mixture, mixed with an organic solvent such as N-methylpyrrolidone or toluene or water to prepare a paste, and then applied the obtained paste onto the positive electrode current collector And it can form by adjusting a density and thickness by drying, a roll press, etc. Known methods and conditions such as coating and drying may be employed.

[Positive electrode mixture layer]
In the positive electrode plate of the present invention, the positive electrode mixture layer is provided on the intermediate layer and contains a positive electrode active material and a binder.

  In the present invention, the positive electrode mixture layer has a porosity set to 39% or less. By setting the porosity of the positive electrode mixture layer to 39% or less, the contact amount of the non-aqueous electrolyte to the intermediate layer (that is, the non-aqueous electrolytic mass permeating the intermediate layer) is reduced, and as a result, The swelling start temperature of the intermediate layer is shifted to the high temperature side, and the rise start temperature of the internal resistance can be increased. From the viewpoint of more effectively increasing the internal resistance rise start temperature, the porosity of the positive electrode mixture layer is preferably 30% or less.

  The lower limit of the porosity of the positive electrode mixture layer is not particularly limited, but preferably 15% or more, more preferably 20% or more, from the viewpoint of providing excellent workability. If the porosity of the positive electrode mixture layer is less than 15%, the positive electrode plate tends to be broken and tends to be difficult to wind.

  In the present invention, the porosity of the positive electrode mixture layer is a value in the positive electrode mixture layer in the final state of discharge (completely discharged state). The positive electrode plate in a state before the electrolyte solution is injected is in a discharged state, and can be directly used for measurement of the porosity. In addition, the positive electrode plate included in the completed electric storage element is measured in a state where the electric storage element is sufficiently discharged at a discharge current of 0.1 C or less, the positive electrode plate is taken out, and the electrolytic solution is sufficiently removed. It is necessary. In the present invention, the porosity of the positive electrode mixture layer is a value in a dry state, specifically, a measured value after the positive electrode plate is vacuum dried at 100 ° C. for 14 hours.

Specifically, the porosity of the positive electrode mixture layer is determined according to the following formula.
Porosity (%) = (Void volume of positive electrode mixture layer / volume of positive electrode mixture layer) × 100

  In addition, the void | hole volume and volume of a positive mix layer are measured by the mercury intrusion method using a mercury porosimeter.

  The porosity of the positive electrode mixture layer can be controlled by adjusting the thickness in accordance with the composition of the positive electrode mixture layer and the coating mass (mass per unit area of the positive electrode mixture layer). Specifically, the thickness of the positive electrode mixture layer is adjusted by adjusting the pressing pressure and gap (gap of the press part) to the positive electrode mixture layer coated and dried on the intermediate layer. By doing so, a desired porosity can be provided. If the same gap is set, the higher the press pressure, the thinner the positive electrode mixture layer, and the lower the porosity of the positive electrode mixture layer. The lower the press pressure, the thicker the positive electrode mixture layer. The porosity of the positive electrode mixture layer can be increased.

  About the kind of positive electrode active material used for a positive mix layer, it sets suitably according to the kind of nonaqueous electrolyte electrical storage element which uses the positive electrode plate of this invention.

For example, when the positive electrode plate of the present invention is used for a nonaqueous electrolyte secondary battery, the positive electrode active material may be any material that can reversibly occlude and release lithium ions, sodium ions, etc., and may be an inorganic compound. Further, it may be an organic compound. Specific examples of the inorganic compound used as the positive electrode active material for the nonaqueous electrolyte lithium secondary battery include a lithium nickel composite oxide (eg, Li _x NiO ₂ ) and a lithium cobalt composite oxide (eg, Li _x CoO). ₂ ), lithium nickel cobalt composite oxide (eg, LiNi _1-y Co _y O ₂ etc.), lithium nickel cobalt manganese composite oxide (eg, LiNi _x Co _y Mn _1-xy O ₂ , Liα [Ni _x Co _y Mn _1-xy ] _1- αO ₂ etc.), spinel type lithium manganese composite oxide (Li _x Mn ₂ O ₄ etc.), lithium phosphorus oxide having an olivine structure (eg Li _x FePO ₄ , Li _x Fe _1-y Mn _y PO ₄ , Li _x CoPO _4, etc.). Specific examples of the organic compound used as the positive electrode active material for the nonaqueous electrolyte secondary battery include conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, and carbon fluoride.

  In addition, for example, when the positive electrode plate of the present invention is used for a lithium ion capacitor, the positive electrode active material is not particularly limited as long as it can be used as a positive electrode active material of an electric double layer capacitor. In addition to organic compounds, carbon materials such as activated carbon can be used.

  In the positive electrode plate of the present invention, the positive electrode active material may be used alone or in combination of two or more.

  Although it does not restrict | limit especially as content of the positive electrode active material in a positive mix layer, For example, a positive electrode active material is 50-98.9 mass% per total amount of a positive mix layer, Preferably it is 70-97.5 mass%. More preferably, 85-97 mass% is mentioned.

  The binder used for the positive electrode mixture layer may be any binder that can be used as a binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer. And vinylidene fluoride-containing copolymers such as styrene-butadiene rubber (SBR), polyacrylonitrile, and fluororubber. These binders may be used individually by 1 type, and may be used in combination of 2 or more type.

  Although it does not restrict | limit especially as content of the binder in a positive mix layer, For example, a binder is 1-25 mass% per total amount of a positive mix layer, Preferably it is 2-15 mass%, More preferably, 2-7. 5 mass% is mentioned.

  The positive electrode mixture layer may contain a conductive agent, if necessary, in addition to the positive electrode active material and the binder. About the kind of electrically conductive agent used for a positive mix layer, it is the same as that of what is mix | blended with the said intermediate | middle layer. Among these, acetylene black is preferable from the viewpoints of electron conductivity and coatability.

  When the conductive agent is contained in the positive electrode mixture layer, the content thereof is not particularly limited. For example, the conductive agent is 0.1 to 25% by mass, preferably 0.5 to 0.5%, based on the total amount of the positive electrode mixture layer. 15 mass%, More preferably, 1-7.5 mass% is mentioned.

  The positive electrode mixture layer may further contain additives such as a thickener and a filler as necessary. About the kind of these additives, it is the same as that of what is mix | blended with the said intermediate | middle layer.

Although it does not restrict | limit especially about the mass per unit area of a positive mix layer, For example, 0.5-2.5 g / 100cm < ² >, Preferably 1.5-2.5g / 100cm < ² > is mentioned. By satisfying such a mass per unit area, it is possible to provide a non-aqueous electrolyte storage element that is excellent in workability of the positive electrode plate and has a good balance of energy density, charge / discharge rate characteristics, and the like.

  The thickness of the positive electrode mixture layer may be in a range that can satisfy the porosity described above, and is, for example, 15 to 160 μm or less, preferably 35 to 130 μm, and more preferably 35 to 110 μm. In addition, the thickness of the positive mix layer shown here refers to the thickness of the positive mix layer per one side of a positive electrode plate.

  The positive electrode mixture layer was prepared by mixing the constituent components with an organic solvent such as N-methylpyrrolidone and toluene or water, and then applying the obtained paste onto the intermediate layer and drying. It can be formed by adjusting the pressing pressure so that the positive electrode mixture layer has a desired porosity and pressing with a roll press or the like. Known methods and conditions such as coating and drying may be employed.

2. Non-aqueous electrolyte storage element The non-aqueous electrolyte storage element of the present invention includes the positive electrode plate. As described above, in the non-aqueous electrolyte storage element, by using the positive electrode plate, it is possible to increase the temperature at which the internal resistance starts to rise, and to suppress deterioration in durability and input / output characteristics in a high temperature range within the normal use temperature range. Is possible.

  Specific examples of the nonaqueous electrolyte storage element of the present invention include a nonaqueous electrolyte secondary battery and a lithium ion capacitor.

  In addition to the positive electrode plate, the non-aqueous electrolyte electricity storage element of the present invention functions as a non-aqueous electrolyte electricity storage element, and includes a negative electrode plate, a non-aqueous electrolyte, and a separator disposed between the positive electrode plate and the negative electrode plate. As long as it has. Hereafter, the member which comprises the nonaqueous electrolyte electrical storage element of this invention is demonstrated in detail.

[Negative electrode plate]
The negative electrode plate should just have the negative mix layer formed on the negative electrode collector.

  Although it does not restrict | limit especially as a negative electrode collector used for a negative electrode, For example, metal materials, such as copper, nickel, stainless steel, nickel plating steel, chromium plating steel, are mentioned. Among these, copper is preferable from the viewpoint of ease of processing and cost.

  The negative electrode mixture layer includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions, sodium ions, and the like. Specifically, the negative electrode active material used in the non-aqueous electrolyte secondary battery includes amorphous carbon such as non-graphitizable carbon (hard carbon) and graphitizable carbon (soft carbon); graphite; Al, Alloys of metals such as Si, Pb, Sn, Zn, Cd and lithium; silicon oxide; tungsten oxide; molybdenum oxide; iron sulfide; titanium sulfide; Moreover, specifically, activated carbon is mentioned as a negative electrode active material used for a lithium ion capacitor. These negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

  In addition to the negative electrode active material, the negative electrode mixture layer may contain additives such as a conductive agent, a binder, a thickener, and a filler as necessary. About the kind of these additives, it is the same as that of what is mix | blended with a positive mix layer.

  The negative electrode plate was prepared by mixing the constituents of the negative electrode mixture layer with an organic solvent such as N-methylpyrrolidone and toluene or water, and preparing the paste, and then coating the obtained paste on the negative electrode current collector. And it can form by adjusting the density and thickness of a negative mix layer by drying, a roll press, etc. Known methods and conditions such as coating and drying may be employed.

[Nonaqueous electrolyte]
The non-aqueous solvent used in the non-aqueous electrolyte is not particularly limited, and examples thereof include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, vinylene carbonate; γ-butyrolactone, γ-valerolactone Cyclic esters such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; chain esters such as methyl formate, methyl acetate and methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3-dioxane, 1, Ethers such as 4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane and methyldiglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or derivatives thereof; ethylene sulfide, sulfur Examples include holan, sultone, and derivatives thereof. These non-aqueous solvents may be used alone or in combination of two or more.

The supporting salt used for the non-aqueous electrolyte is not particularly limited, and lithium salts that are stable in a wide potential region generally used for non-aqueous electrolyte secondary batteries can be used. Examples of the supporting salt include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C _{4 F 9 SO 2), LiC} (CF 3 SO 2) 3, LiB (C 2 O 4) 2, LiC (C 2 F 5 SO 2) 3 and the like. These supporting salts may be used alone or in combination of two or more. The content of the supporting salt in the non-aqueous electrolyte is not particularly limited and may be appropriately set according to the type of the supporting salt to be used, the type of the non-aqueous solvent, and the like. For example, 0.1 to 5.0 mol / L Preferably, 0.8-2.0 mol / L is mentioned.

[Separator]
The separator is not particularly limited as long as it has insulating properties, and a microporous film or a nonwoven fabric is used. Examples of the material constituting the separator include polyolefin resins such as polyethylene and polypropylene, polyimide resins, and celluloses. These materials may be used individually by 1 type, and may be used in combination of 2 or more type.

[Other components]
Further, in the nonaqueous electrolyte storage element, other components include a terminal, an insulating plate, a case, etc., but in the nonaqueous electrolyte storage element of the present invention, these components are used as they are. It can be used.

[Structure of nonaqueous electrolyte storage element]
FIG. 2 is a schematic view of a rectangular nonaqueous electrolyte storage element 1 which is an embodiment of the nonaqueous electrolyte storage element of the present invention. In the figure, the inside of the container is seen through. In the non-aqueous electrolyte storage element 1 shown in FIG. 2, the electrode group 2 is housed in an exterior body 3. The electrode group 2 is formed by winding the positive electrode for a nonaqueous electrolyte electricity storage device of the present invention and the negative electrode containing a negative electrode active material through a separator. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4 ′, and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5 ′.

  The configuration of the non-aqueous electrolyte storage element of the present invention is not particularly limited, and examples thereof include cylindrical, square (rectangular), and flat storage elements.

[Production method]
The nonaqueous electrolyte storage element of the present invention is manufactured by sandwiching a separator between a positive electrode plate and a negative electrode plate and impregnating them with a nonaqueous electrolyte.

3. Power Storage Device A power storage device according to the present invention includes the nonaqueous electrolyte power storage element. In the present invention, the power storage device is a device that uses the non-aqueous electrolyte power storage element to supply electric power to a power source that operates with electric energy, or is supplied with electric power from the power source. In addition to the electrolyte storage element, an electronic control unit or the like may be provided as needed to control the non-aqueous electrolyte storage element.

  The power storage device of the present invention may include one non-aqueous electrolyte storage element or a plurality of the non-aqueous electrolyte storage elements.

  One embodiment of the power storage device of the present invention is shown in FIG. In FIG. 3, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of non-aqueous electrolyte power storage elements 1. The power storage device 30 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV).

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is limited to these Examples and is not interpreted. In addition, the porosity of the positive mix layer shown below is a value measured according to the method described above.

1. Manufacture of positive electrode plates for lithium secondary batteries
Example 1
A paste for an intermediate layer containing 30 parts by mass of a conductive agent (acetylene black), a fluororesin binder (PVDF, average molecular weight 280,000), and a non-aqueous solvent (N-methylpyrrolidone; NMP) was produced. The intermediate layer paste was prepared through a kneading step using a multi-blender mill by adjusting the amount of NMP to adjust the solid content concentration to 14% by mass. This intermediate layer paste was applied to one side of a current collector (aluminum foil) having a thickness of 20 μm so that the application mass (intermediate layer mass per unit area) was 0.03 g / 100 cm ² . A current collector provided with an intermediate layer was produced by evaporating and drying NMP in a thermostatic bath.

Next, 94 parts by mass of a positive electrode active material (lithium nickel manganese cobalt composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ )), 3 parts by mass of a conductive agent (acetylene black), and a binder (PVDF A paste for a positive electrode mixture layer containing 3 parts by mass of an average molecular weight of 280,000) and a non-aqueous solvent (NMP) was prepared. The paste for the positive electrode mixture layer was prepared through a kneading process using a multi-blender mill by adjusting the amount of NMP to adjust the solid content to 68% by mass. This paste for the positive electrode mixture layer was applied on the intermediate layer so as to have a coating mass (positive electrode mixture layer mass per unit area) of 2.0 g / 100 cm ^2, and NMP was applied in a constant temperature bath at 100 ° C. Evaporated to dryness. Next, roll pressing was performed so that the porosity of the positive electrode mixture layer was 39%, and a positive electrode plate was produced by cutting out into a circular shape having a diameter of 1.4 cm. The thickness of the intermediate layer of the produced positive electrode plate (the thickness of the portion sandwiched between the current collector and the positive electrode mixture layer, the same applies to Example 2 and Comparative Example 1 below) is 2 μm, and the thickness of the positive electrode mixture layer Was 105 μm. The positive electrode plate was vacuum dried (temperature 100 ° C., 14 hours) and then used for resistance measurement described later.

Example 2
A positive electrode plate was prepared under the same conditions as in Example 1 except that the roll press conditions were changed so that the porosity of the positive electrode mixture layer was 26%. The thickness of the intermediate layer of the produced positive electrode plate was 2 μm, the thickness of the positive electrode mixture layer was 93 μm, and the porosity of the positive electrode mixture layer was 26%. The positive electrode plate was vacuum dried (temperature 100 ° C., 14 hours) and then used for resistance measurement described later.

Comparative Example 1
A positive electrode plate was prepared under the same conditions as in Example 1 except that the roll press was not performed. The thickness of the intermediate layer of the produced positive electrode plate was 3 μm, the thickness of the positive electrode mixture layer was 135 μm, and the porosity of the positive electrode mixture layer was 55%. The positive electrode plate was vacuum dried (temperature 100 ° C., 14 hours) and then used for resistance measurement described later.

2. Measurement of electrode resistance
Method for Producing Resistance Measurement Cell Tomcell (manufactured by Nippon Tomcell Co., Ltd.) was used for measuring the resistance of the electrode. This tom cell is composed of a lower lid, an electrode plate, a separator, an electrode plate, a disk, a leaf spring, and an upper lid. On the inside of the packing existing on the stainless steel bottom lid, a separator was placed between two positive electrode plates previously immersed in a non-aqueous electrolyte. At this time, the active material application surfaces of the positive electrode plates were made to face each other. After that, a stainless steel disk and a leaf spring were placed, and finally a stainless steel upper lid was placed, and then tightened and fixed with a nut. The tightening pressure at this time was 0.5 Nm.

The nonaqueous electrolyte and separator used are as follows.
[Nonaqueous electrolyte]
In a mixed solvent in which ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) are mixed at a volume ratio of 30:35:35, lithium hexafluorophosphate (LiPF) which is a fluorine-containing electrolyte salt is used. ₆ ) was dissolved at a concentration of 1.0 mol / l to prepare a non-aqueous electrolyte. The amount of water in the non-aqueous electrolyte was less than 50 ppm.

[Separator]
As the separator, a 30 μm thick polyethylene microporous film having an air permeability of about 600 seconds / 100 cc and processed into a circle having a diameter of 1.6 cm was used.

Electrode Resistance Measurement Method A measuring cell was placed in a thermostatic bath, and an AC resistance of 1 kHz (amplitude 5 mV) was measured while raising the temperature of the thermostatic bath at 3 ° C./min. As the cell temperature, the temperature obtained by a temperature measuring terminal installed on the upper surface of the cell was recorded. The AC resistance measurement was performed using a device combining a 1287 type potentio / galvanostat made by Solartron and a 1260 type frequency response analyzer.

3. The results obtained are shown in Table 1. In any of the positive electrode plates of Examples 1 and 2 and Comparative Example 1, the starting point of increase in internal resistance was observed in the temperature range of 75 ° C. or higher. However, when the porosity of the positive electrode mixture layer was 39% or less ( In Examples 1 and 2), the temperature at which the internal resistance started to increase was higher than when the porosity of the positive electrode mixture layer was 55%.

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte storage element 2 Electrode group 3 Exterior body 4 Positive electrode terminal 4 ′ Positive electrode lead 5 Negative electrode terminal 5 ′ Negative electrode lead 11 Positive electrode current collector 12 Intermediate layer 13 Positive electrode mixture layer 20 Power storage unit 30 Power storage device

Claims (6)

A positive electrode current collector, a positive electrode mixture layer containing a positive electrode active material, and an intermediate layer located between the positive electrode current collector and the positive electrode mixture layer,
The intermediate layer includes a conductive agent and a fluorine-containing resin binder,
The positive electrode plate for a nonaqueous electrolyte storage element, wherein the positive electrode mixture layer has a porosity of 39% or less.   The positive electrode plate for nonaqueous electrolyte electricity storage elements according to claim 1, wherein the porosity of the positive electrode mixture layer is 15 to 39%.   The positive electrode plate for nonaqueous electrolyte electricity storage elements according to claim 1 or 2, wherein the fluororesin binder is polyvinylidene fluoride. The coating amount of the positive electrode mixture layer is 0.5 to 2.5 g / 100 cm ^2, the non-aqueous electrolyte energy storage device for the positive electrode plate according to claim 1.   A nonaqueous electrolyte storage element comprising the positive electrode plate for a nonaqueous electrolyte storage element according to claim 1.   A power storage device comprising the nonaqueous electrolyte power storage element according to claim 5.

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